1 The dataset

1.1 The networks

From the overall dataset of the Aspe database, only 3 monitoring networks are considered here.

  • Réseau de Contrôle de Surveillance (RCS)
  • Réseau Hydrobiologique Piscicole (RHP)
  • Réseau de Référence Pérenne (RRP)

The former two are monitoring networks considered representative of the diversity of the rivers ecosystems in continental France and operated unmodified since 2007. Pooled together, they are further referred to as “REPNET”. The RRP (perennial reference network) encompasses only minimally-impacted sites. It is operated unmodified since 2013, and further referred to as “REFNET”.

Note that one site can contribute to more than one network (true also for one survey).

1.2 Data selection

A first selection is made to keep only the surveys:

  • belonging to REPNET (since 2007) and REFNET (since 2013)
  • with FBI rating

Then, we selected only the surveys on the sites surveyed annually or bi-annually.

Eventually, our dataset covers 16023 surveys carried out on 1583 sites.

Venn diagram showing the number of sampling sites belonging to the reference network, to the monitoring networks and to both.

Figure 1.1: Venn diagram showing the number of sampling sites belonging to the reference network, to the monitoring networks and to both.

Are the sampling sites distributed evenly in space?

Map of mainland France distinguishing the reference and monitoring networks. A single point can be on both maps.

Figure 1.2: Map of mainland France distinguishing the reference and monitoring networks. A single point can be on both maps.

1.3 Sampling effort across time

Is the sampling effort constant in time?

Annual number of sites surveyed.

Figure 1.3: Annual number of sites surveyed.

2 Fish-based Index

2.1 REFNET vs. REPNET

On the overall dataset, the percentages of surveys with a FBI score “Good” or above (i.e. FBI < 16) is:

network

pc_good_or_better

REFNET

0.7742656

REPNET

0.5504029

2.2 Nationwide trend

Is there a temporal trend in FBI? Do the trends differ between reference and non-refence sites?

Fish-based Index temporal trends for the sites belonging to the reference and monitoring networks. For each serie, the points and solid lines represent the annual median value across sites and the ribbon is the interquartile range.

Figure 2.1: Fish-based Index temporal trends for the sites belonging to the reference and monitoring networks. For each serie, the points and solid lines represent the annual median value across sites and the ribbon is the interquartile range.

Testing the trends significance for each of the percentiles:

Temporal trend in FBI scores annual 25, 50 and 75 percentiles across the sites for REPNET and REFNET. Solid regression lines indicate that the Mann-Kendall trend test is significant at the 5% threshold.

Figure 2.2: Temporal trend in FBI scores annual 25, 50 and 75 percentiles across the sites for REPNET and REFNET. Solid regression lines indicate that the Mann-Kendall trend test is significant at the 5% threshold.

Temporal trend in the annual percentage of sites with 'high' or 'good' integrity according to the FBI for REPNET and REFNET. The solid regression line indicates that the Mann-Kendall trend test is significant at the 5% threshold.

Figure 2.3: Temporal trend in the annual percentage of sites with ‘high’ or ‘good’ integrity according to the FBI for REPNET and REFNET. The solid regression line indicates that the Mann-Kendall trend test is significant at the 5% threshold.

NB: In the table below, trends are interpreted differently for the percentage of sites in ‘good condition’ (for which an increase indicated improvement) and for the percentiles (for which an increase indicates a degradation).

This table indicates that the slopes are not significant whatever the percentile and the network. However, for REFNET, p75 is close to the 5% threshold (p = 0.07) with an increasing trend (positive slope, i.e. degradation) and the percentage of sites in ‘good condition’ significantly decreases (negative slope, i.e. degradation). Both are congruent with a degradation trend in reference sites.

2.3 Test of slope for REPNET 2013-2023

Merge the tables above.

Table 2.1: Mann-Kendall test of monotonic temporal trend for the 25, 50 and 75 percentiles of annual FBI score for REPNET, 2013-2013, along with the percentage of sites in ‘good’ condition. The rows in bold indicate a significant trend (mk_pvalue < 0.05).

network

period

variable

mk_pvalue

sens_slope

sig

trend

REFNET

2013-2023

p25

0.043

0.0682

TRUE

Degradation

REFNET

2013-2023

p50

0.119

0.0823

FALSE

Non-significant

REFNET

2013-2023

p75

0.008

0.1225

TRUE

Degradation

REFNET

2013-2023

pc_good

0.003

-0.0059

TRUE

Degradation

REPNET

2007-2023

p25

0.837

0.0021

FALSE

Non-significant

REPNET

2007-2023

p50

0.343

0.0257

FALSE

Non-significant

REPNET

2007-2023

p75

0.837

-0.0166

FALSE

Non-significant

REPNET

2007-2023

pc_good

0.837

0.0001

FALSE

Non-significant

REPNET

2013-2023

p25

0.161

0.0328

FALSE

Non-significant

REPNET

2013-2023

p50

0.008

0.0619

TRUE

Degradation

REPNET

2013-2023

p75

0.008

0.1436

TRUE

Degradation

REPNET

2013-2023

pc_good

0.119

-0.0024

FALSE

Non-significant

2.4 Test of the slope for 2013-2023 without shared sites

In the following table, the analysis is the same as above apart from the fact that the 125 sites that are shared between REPNET and REFNET have been excluded. This is made to verify that the common trends observed on REFNET and REPNET are not driven by these common sites.

Table 2.2: Mann-Kendall test of monotonic temporal trend for the 25, 50 and 75 percentiles of annual FBI score for REPNET and REFNET, 2013-2013, excluding the sites that are shared between these networks. The rows in bold indicate a significant trend (mk_pvalue < 0.05).

network

period

variable

mk_pvalue

sens_slope

sig

trend

REFNET

2013-2023

p25

0.020

0.1233

TRUE

Degradation

REFNET

2013-2023

p50

0.062

0.0992

FALSE

No trend

REFNET

2013-2023

p75

0.008

0.1422

TRUE

Degradation

REPNET

2013-2023

p25

0.020

0.0635

TRUE

Degradation

REPNET

2013-2023

p50

0.436

0.0428

FALSE

No trend

REPNET

2013-2023

p75

0.043

0.1355

TRUE

Degradation

3 FBI metrics

Do the FBI functional metrics display temporal trends?

Temporal trend in FBI metrics annual median across the sites for REPNET and REFNET. Solid regression lines indicate that the Mann-Kendall trend test is significant at the 5% threshold.

Figure 3.1: Temporal trend in FBI metrics annual median across the sites for REPNET and REFNET. Solid regression lines indicate that the Mann-Kendall trend test is significant at the 5% threshold.

6 Save output